US4270991AExpiredUtility

Anodic oxidation of aluminum and aluminum alloys with a lignin electrolyte solution

37
Individually held — no corporate assignee on recordPriority: May 20, 1977Filed: May 20, 1977Granted: Jun 2, 1981
Est. expiryMay 20, 1997(expired)· nominal 20-yr term from priority
Inventors:Jack L. Woods
C25D 11/06
37
PatentIndex Score
4
Cited by
4
References
8
Claims

Abstract

Aluminum and its alloys are anodized with a hard finish by enhancing the anodizining electrolyte solution with a lignin or lignosulfonate salt.

Claims

exact text as granted — not AI-modified
What is claimed is: 
     
       1. An electrolyte process for hard anodizing aluminum and aluminum alloys which comprises making an aluminum or aluminum alloy article anode in an acid electrolyte solution containing between 0.50 and 5.0 grams per liter of electrolyte solution of a lignin selected from the group consisting of lignin, a ligno sulfonic acid and a ligno sulfonate salt and an acid concentration between 60 and 350 grams per liter at a temperature between the freezing point of the electrolyte solution and 10° C. 
     
     
       2. A process according to claim 1 wherein the current is a direct current. 
     
     
       3. A process according to claim 2 wherein the lignin is a lignin extracted from wood. 
     
     
       4. A process according to claim 2 wherein the lignin is a ligno sulfonic acid. 
     
     
       5. A process according to claim 4 wherein the lignin is a salt of a ligno sulfonic acid. 
     
     
       6. A process according to claim 5 wherein the lignin is a sodium ligno sulfonate. 
     
     
       7. A process according to claim 5 wherein the lignin is an ammonium ligno sulfonate. 
     
     
       8. A process according to claim 1 wherein the current is a pulsated direct current.

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